Novel light emitting layers for LED devices based on high Tg polymer matrix compositions

ABSTRACT

A light emitting device includes: (a) a light emitting layer including an electroluminescent organic material dispersed in a matrix, wherein the matrix contains a non-electroluminescent organic polymer having a T g  of at least 170° C., and each of the organic polymer and the electroluminescent organic material constitutes at least 20 percent by weight of the light emitting layer; and (b) electrodes in electrical communication with the light emitting layer and configured to conduct an electric charge through the light emitting layer such that the light emitting layer emits light. A method for manufacturing a flexible organic light emitting device, includes providing the light emitting layer and providing electrodes above and below the light emitting layer, wherein the electrodes are in electrical communication with the light emitting layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. Ser. No. 10/253,108, filed Sep.23, 2002, having the same title, which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

This invention relates to organic electroluminescent devices and morespecifically to light-emitting layer compositions.

Light emitting diode (LED) technology is expected to be a majoropportunity for advanced materials development impacting a large numberof future technology based applications. These include flat paneldisplays which offer significant advantages over liquid crystal displays(LCDs) including much lower power requirements, improved definition,broader viewing angles and faster response times. The technology forLEDs offers the potential for lower cost lighting sources compared toincandescent lighting as well as fluorescent lighting applications.Inorganic based LEDs are already replacing some of these conventionalapplications including traffic lighting as well as flashlights offeringequal or improved lighting at much lower power requirements.

Small molecule organic light emitting diodes (SMOLEDs) are beingcommercialized to replace LCD displays based on lower powerrequirements, faster response times, better definition and also easierfabrication. Such SMOLEDs are expected to revolutionize the flat paneldisplay technology. Another area receiving considerable interestinvolves polymeric light emitting diodes (PLEDs) where polymeric lightemitting materials can be utilized for flexible organic light emittingdiodes (FOLEDs). A significant advantage of polymeric materials involvesthe fabrication possibilities. FOLEDs offer the potential for ink-jetprinting of flat panel displays on flexible substrates such asindium-tin oxide coated polymeric films (i.e. poly(ethyleneterephthalate)(PET), oriented polypropylene or polycarbonate). Roll toroll printing processes could also be utilized for FOLEDs. The potentialfor FOLEDs is considered to be quite large offering unique flat orcontoured display panels. These FOLEDs may be of interest for uniquelighting applications and large screen displays. These displays would below cost, easy to install, very thin and power efficient. An examplecould be a battery operated TV screen, which would be the thickness ofseveral sheets of paper and capable of folding, at a cost commensuratewith the fabrication simplicity. Of course many problems have to besolved before these possibilities become reality.

Development of PLEDs has focused on polymeric materials which exhibitelectroluminescence. These materials are generally conjugated polymers,such as poly(phenylene vinylene), polyfluorenes, polyphenylenes,polythiophenes and combinations of such structures. Conjugated polymersfor use in PLEDs are disclosed by a number of references. See, e.g.,U.S. Pat. No. 5,247,190 to Friend et al., U.S. Pat. No. 5,900,327 to Peiet al. and Andersson et al., J. Mater Chem., 9,1933-1940 (1999).

Variations of conjugated polymers useful for PLEDs include polymerscomprised of oligomeric units of conjugated structures coupled into ahigh molecular weight polymer. See, e.g., U.S. Pat. No. 5,376,456 toCumming et al., U.S. Pat. No. 5,609,970 to Kolb et al., Pinto et al.,Polymer, 41, 2603-2611 (2000) and U.S. Pat. No. 6,030,550 toAngelopoulos et al.

A large number of low molecular weight compounds exist which exhibitfluorescence and electroluminescence. Some of these materials arecommonly referred to as laser dyes. Many of these compounds offer veryhigh fluorescence and thus electroluminescence. However, the propertiesdesired for LED applications are generally only observed in solution orat low levels of doping in electro-optical or electroactive polymers. Inthe solid state, these materials can crystallize and lack the mechanicalintegrity to be utilized in PLEDs or SMOLEDs. Additionally (and moreimportantly), the excellent fluorescence and electroluminescence is lostwith crystallization. These problems have been well documented invarious reviews on the subjects of materials for LEDs. See, e.g., Kelly,“Flat Panel Displays. Advanced Organic Materials.” (Royal Society ofChemistry, 2000) at pp.155 and 177. Consequently, a number of attemptshave been made to solve these problems.

For example, U.S. Pat. No.6,329,082 to Kreuder et al. discloseshetero-spiro compounds suitable for use in LED devices. The compoundspurportedly overcome “the unsatisfactory film-forming properties and . .. pronounced tendency to crystallize” of conventional low molecularweight fluorescent materials.

U.S. Pat. No. 6,214,481 to Sakai et al. purports to address problemswith low emission intensity in solution and thermal instability of OLEDsby providing an organic host compound (e.g., distyrylarylenederivatives) for a fluorescent substance, wherein the host compound hasa fluorescent quantum efficiency of at least 0.3 in a solid state and aT_(g) of at least 75° C.

Examples exist where fluorescent dopants are included in electroactivecomponents of LEDs. See, e.g., Shoustikov et al., IEEE Journal ofSelected Topics in Quantum Electronics, Vol. 4, No.1 (1998), Djurovichet al., Polymer Preprints, 41(1), 770 (2000), Chen et al., PolymerPreprints 41(1), 835 (2000), U.S. Pat. No. 6,303,239 to Arai, U.S. Pat.No. 4,769,292 to Tang et al., U.S. Pat. No. 6,329,086 to Shi et al.,U.S. Pat. No.5,928,802 to Shi et al., and Hu et al., J. Appl. Phys.,83(11) 6002 (1998).

Examples also exist in the literature where fluorescent dyes have beenadded to non-active polymers for various applications. See, e.g.,Quaranta et al., Synthetic Metals, 124, 75-77 (2001), Muller et al.,Polymer Preprints, 41(1), 810 (2000), Sisk et al., Chemical Innovation,May 2000, U.S. Pat. No. 6,067,186 to Dalton et al., Kocher et al.,Advanced Functional Materials, 11 (1), 31 (2001) and U.S. Pat.No.5,952,778 to Haskal et al.

There are a number of examples in the literature where non-activepolymers have been modified by side chain or main chain incorporation ofoptically active species. See, e.g., Hwang et al., Polymer, 41,6581-6587 (2000), U.S. Pat. No.5,414,069 to Cumming et al., U.S. Pat.No. 6,103,446 to Devlin et al., and U.S. patent application PublicationUS 2001/0026879 Al to Chen et al.

U.S. Pat. No. 6,277,504 to Koch et al. discusses an electroluminescentassembly comprising a component which is a substituted or unsubstituted1,3,5-tris(aminophenyl)benzene and a luminescent compound based onsubstituted metal complexed hydroxyquinoline compounds. Theelectroluminescent assembly can further comprise a polymeric binder.Similarly, U.S. Pat. No. 6,294,273 to Heuer et al. discloses a polymericbinder for the electroluminescent compound of a metal complex ofN-alkyl-2,2′-imino-bis(8-hydroxy-quinoline).

Various references note blends of active electroluminescent polymers forutility in LED devices offering in many cases improved performance overthe individual constituents. See, e.g., Hu et al., J. Appl. Phys.,76(4), 2419 (1994), and Yang et al., Macromol. Symp., 124, 83-87 (1997).

Blends of fluorene-based alternating polymer with non-active polymers(e.g. PMMA, epoxy resin, polystyrene) are disclosed in U.S. Pat.No.5,876,864 to Kim et al. U.S. Pat. No. 6,255,449 to Woo et al. notesthe utility of blends of specific fluorene containing polymers and alitany of other polymers, including conjugated polymers.

Frederiksen et al., J. Mater. Chem., 4(5), 675-678 (1994) teaches theaddition of laser dyes to a polystyrene matrix for use in a LED device.

U.S. Pat. No.5,821,003 to Uemura et al. notes the use of polymericbinders for low molecular weight hole transport materials for the holetransport layer of LED devices. Examples include polysulfone andaromatic tertiary amines. The inclusion of minor amounts of fluorescentcompounds in the polymer bound hole transport layer is noted to improvethe luminance of blue and white.

U.S. Pat. No.5,663,573 discloses the use of a variety of organic lightemitting materials for preparing a bipolar electroluminescent device,including polypyridines, polypyridylvinylenes, polythiophenes,polyphenylenes, polyphenylenevinylenes, polyphenylenebenzobisthiazoles,polybenzimidazobenzophenanthrolines, polyfluorenes, polyvinylcarbazoles,polynaphthalenevinylenes, polythienylenevinylenes,polyphenylene-acetylenes, polyphenylenediacetylenes andpolycyanoterephthalylidenes.

Despite the foregoing developments, it is desired to incorporate theexcellent properties of low molecular weight electroluminescentmaterials such as laser dyes as a material which could be utilized in aLED device with fabrication characteristics typically exhibited by PLEDsand the crystallization behavior characteristic of these materialseffectively eliminated.

All references cited herein are incorporated herein by reference intheir entireties.

BRIEF SUMMARY OF THE INVENTION

Accordingly, the invention provides a light emitting device comprising:

-   -   a light emitting layer comprising an electroluminescent organic        material dispersed in a matrix, wherein the electroluminescent        organic material has a molecular weight less than about 2000        amu, the matrix comprises a non-electroluminescent organic        polymer having a T_(g) of at least 170° C., and each of the        non-electroluminescent organic polymer and the        electroluminescent organic material constitutes at least 20        percent by weight of the light emitting layer; and    -   electrodes in electrical communication with the light emitting        layer and configured to conduct an electric charge through the        light emitting layer such that the light emitting layer emits        light.

Further provided is a method for manufacturing a light emitting device,comprising providing the light emitting layer; and providing electrodesin electrical communication with the light emitting layer, wherein theelectrodes are configured to conduct an electric charge through thelight emitting layer such that the light emitting layer emits light.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

The invention will be described in conjunction with the followingdrawings, wherein:

FIG. 1 is a graph of the current-voltage characteristic of Example 21;

FIG. 2 is a graph of the current-voltage characteristic of Example 22;

FIG. 3 is a graph of the current-voltage characteristic of Example 23;

FIG. 4 is a graph of the current-voltage characteristic of Example 24;

FIG. 5 is a graph of the current-voltage characteristic of Example 25;and

FIG. 6 is a graph of the current-voltage characteristic of Example 26.

DETAILED DESCRIPTION OF THE INVENTION

It has been found that the incorporation of low molecular weightsubstances (which exhibit high fluorescence and thuselectroluminescence) in high T_(g) polymers allows for the preparationof thin films without crystallization of the low molecular weightsubstances. The resulting films exhibit high fluorescence and thuselectroluminescence as solid materials. Lower T_(g) polymers areinadequate for this application as the level of electroluminescentmaterial incorporation will not be sufficient to yield theelectroluminescent efficiency required due to the resultant T_(g) of thepolymer/electroluminescent material mixture being lower than thatrequired for long term stability. For example, in the case of laserdyes, which are one class of low molecular weight electroluminescentmaterials, the rate of crystallization of the laser dyes (whichcharacteristically exhibit crystallinity) is dependent upon the T_(g) ofthe polymer/laser dye mixture. In the fabrication or use of FOLEDdevices, temperatures in excess of room temperature will certainly occurand if the T_(g) of the polymer/laser dye is exceeded, crystallizationof the laser dye could occur thus limiting the electroluminescentefficiency of the device. It has been found that high T_(g) polymers canbe utilized to prevent the crystallization of laser dyes even when thelaser dye concentration is in excess of 50 wt. % based on the weight ofthe light emitting film.

Organic Polymers

The light emitting layer of the invention comprises an organic polymerhaving a T_(g) of at least 170° C., preferably at least 200° C. Thus,the expression “high T_(g) polymers” as used herein means polymershaving a glass transition temperature of at least 170° C. The organicpolymer preferably constitutes about 20 to about 80 wt. % of the lightemitting layer, and in some of these preferred embodiments, constitutesabout 40 to about 60 wt. % of the light emitting layer. Theelectroluminescent material needs to be 20 wt. % or higher in order tohave a percolation pathway for transport of holes and electrons to thelight emitting material. Lower levels do not allow for sufficienttransport to yield desired electroluminescent results.

Suitable organic polymers include but are not limited to: polycarbonatesbased on aromatic bisphenols (at the lower limit of the T_(g)requirement); polysulfones such as the polysulfone from4,4′-dichlorodiphenylsulfone and Bisphenol A (T_(g)˜180° C.), thepoly(phenyl sulfone) from 4,4′-biphenol and 4,4′-dichlorodiphenylsulfone(T_(g)˜220° C.) and other polysulfones based on various bisphenols and4,4′-dichlorodiphenylsulfone, including poly(ether sulfone) from4,4′-dihydroxydiphenylsulfone and ,4′-dichlorodiphenylsulfone(T_(g)˜220° C.); polyimides such as the commercial product Ultem 1000(T_(g)˜220° C.) and variants thereof, and other polyimides (many havingT_(g)'s well in excess of 220° C.) from dianhydrides (particularly fromaromatic dianhydrides such as pyromellitic dianhydride, benzophenonedianhydride, diphenyl ether dianhydride and the like) and diamines(particularly from aromatic diamines such as 4,4′-diaminodiphenylmethane, 4,4′-diamino diphenyl ether and 4,4′-diamino diphenylhexafluoroisopropylidene, p-phenylenediamine, m-phenylenediamine and thelike).

A preferred class of high T_(g) polymers comprises poly(aryl ether)ssuch as those described in U. S. Pat. Nos. 5,658,994 and 5,874,516. Aparticularly preferred polymer from this class of materials is thecondensation polymer from the polymerization of 4,4′-dibromobiphenylwith 9,9-bis(4-hydroxyphenyl)fluorene.

In certain of these embodiments, the poly(arylene ether) comprisesrepeating units of the structure:—(—O—Ar¹—O—Ar²—)m(—O—Ar³—O—Ar⁴—)n—wherein m is 0 to 1, n is 1-m and Ar¹, Ar², Ar³ and Ar⁴ areindependently divalent arylene radicals. In these embodiments, Ar¹, Ar²,Ar³ and Ar⁴ are preferably divalent arylene radicals independentlyselected from the group consisting of:

provided that Ar¹, Ar², Ar³ and Ar⁴ cannot be isomeric equivalents otherthan diradical 9,9-diphenylfluorene. In certain embodiments, m is 0.5and n is 0.5. In certain other embodiments, m is 1 and Ar¹ is biphenylradical.

An advantageous feature of poly(aryl ether)s (as well as certain otherpolymers) is the absence of functional groups (such as carbonyls) in therepeating units, which if present could result in quenching of theelectroluminescence of the electroluminescent low molecular weightcompounds included in the film. Another poly(aryl ether) of interest ispoly(2,6-dimethyl-1,4-phenylene oxide) (T_(g)˜210° C.) and similarstructures with various substitution on the aromatic ring, provided theT_(g) is equal to or greater than 170 ° C. Other poly(aryl ether)sdiscussed in a reference by Robeson et al. (in “Molecular Basis ofTransitions and Relaxations”, edited by Dale J. Meier, Gordon and BreachScience Publishers, New York, pp.405-425) are suitable for use in thepresent invention.

Another class of compounds suitable for use as organic polymers of theinvention involve polyarylates such as those derived from bisphenols(such as Bisphenol A) and tere(iso)phthaloyl chlorides, as well aspolyestercarbonates comprised of the above units of polyarylates andpolycarbonates.

Electroluminescent Materials

The light emitting layer of the invention comprises anelectroluminescent material dispersed in the organic polymer matrix. Theelectroluminescent materials of this invention are defined as materialsthat exhibit electroactive properties in electroluminescentapplications, including the light emitting materials, the hole transportmaterials and the electron transport materials. The electroluminescentmaterials can be combinations of the electroactive species. In apreferred embodiment of this invention, the electroluminescent materialis a combination of a hole transport material, a light emitting materialand an electron transport material. Optionally, the electroluminescentmaterial of this invention can be combinations of a hole transportmaterial and a light emitting material or an electron transport materialand a light emitting material. The electroluminescent materialpreferably constitutes about 20 to about 80 wt. % of the light emittinglayer, and in some of these preferred embodiments, constitutes about 40to about 60 wt. % of the light emitting layer. Lower levels ofelectroluminescent materials might not produce sufficiently intenseelectroluminescence, and higher levels can adversely impact the physicalintegrity of the resulting film.

Suitable electroluminescent materials must be miscible with the highT_(g) polymers of the invention. This will provide increased T_(g) (ofthe active species), greatly improved mechanical properties and filmintegrity, decreased crystallization rates, and the ability to beutilized in spin-on processing, ink-jet printing, and roll-to-rollprinting processes. Suitable electroluminescent materials include butare not limited to fluorescent compounds such as laser dyes as well asother active organic species, including distyrenyl derivatives such asthose described in U.S. Pat. Nos. 5,503,910, 5,121,029 and 6,214,481.

The class of laser dyes includes but is not limited to Coumarin 6,Coumarin 334, Coumarin 343, Rhodamine B, Rhodamine 6G, Rhodamine 110,Fluorescein 548, 2′,7′-dichlorofluorescein, cresyl violet perchlorate,Nile Blue AA perchlorate, p-terphenyl, p-quaterphenyl, Exalite (376,384r, 389), Fluorol 555, Fluorescein Diacetate, Carbostyril 165, IR-140,Thionin, perylene, 9-amino acridine HCl and the like. Additional laserdyes include aromatic methylidine compounds of the general structure:R¹R²C═CH—Ar—CH═CR³R⁴where R¹, R², R³, and R⁴ represent hydrogen, alkyl groups, alkoxygroups, aromatic groups including substituted aromatic groups,cycloaliphatic groups and the like; and Ar represents an aromaticstructure including phenyl, biphenyl, terphenyl linked aromaticstructures including various substituents on the aromatic group(s). Thesubstituents can include alkyl, aryl, alkoxy, hydroxyl, halide, aminoand the like. Such compositions are discussed in various patents issuedto Idemitsu Kosan, including U.S. Pat. Nos. 5,503,910, 5,121,029 and6,214,481.

Quinacridones such as9,18-dihydro-9,18-dimethylbenzo[h]benzo[7,8]quino[2,3-b]acridine-7,16-dione;7,16-dihydro-7,16-dimethylbenzo[a]benzo[5,6]quino[3,2-l]acridine-9,18-dione;N,N′-dimethyl-quinacridone can also be employed as light emittingmaterials in the electroluminescent materials of this invention.

Linked aromatic structures such as 9,10-di-(2-naphthyl)anthracenederivatives as described in U.S. Pat. No. 5,935,721 can also be suitablefor use as the electroluminescent material of the present invention.Light emitting naphthalene derivatives, anthracene derivatives,phenanthrenes, perylenes, chrysenes, butadienes (such astetraphenylbutadiene) and the like are also suitable, as areperiflanthenes as described in U.S. Pat. No. 6,004,685 andtetravinylpyrazines as described in U.S. Pat. No. 5,416,213.

Oligomers of conjugated polymers with molecular weights of less than2000 amu, such as oligophenylene vinylene, oligophenylenevinylene,oligothiophenes such as α-quaterthiophene and α-hexathiophene,oligo(p-phenylene) and oligofluorenes can be suitable light emittingmaterials for the electroluminescent materials of this invention.

The hole transport materials which constitute one of the classes ofelectroluminescent materials of this invention include but are notlimited to aromatic tertiary amines, benzidine, pyrazoline derivativesalong with other classes of known hole transport materials. Suitablearylamine and benzidine derivatives include, e.g.,N,N′-bis(3-methylphenyl)-N,N′-bis(phenyl)-benzidine,N,N′-bis(4-methylphenyl)-N,N′-bis(phenyl)-benzidine,N,N′-di(naphthalene-2-yl)-N,N′-diphenylbenzidine,1,3,-5-tris(3-methyldiphenylamino)benzene;4,4′-Bis(carbazol-9-yl)biphenyl;4,4′,4″-Tris(carbazol-9-yl)-triphenylamine (CAS #139092-78-7);N,N,N′,N′-Tetrakis(3-methylphenyl)-benzidine;4,4′,4″-Tris(N-(2-naphthyl)-N-phenyl-amino)-triphenylamine;4,4′,4″-tris(N,N-diphenyl-amino)-triphenylamine. Suitable pyrazolinederivatives include, e.g., PYR-7 and PYR-9 disclosed by Takeshi Sano etal., J. Mater. Chem., 2000,10 (1), 157-161:

as well as oligothiophenes such as α-quaterthiophene andα-hexathiophene, dibenzochrysene derivatives, oligophenylenevinylenes,oligofluorenes, phthalocyanines and carbazole derivatives.

The electron transport materials, which constitute one of the classes ofelectroluminescent materials of this invention, include but are notlimited to oxadiazole, triazole, phenantroline, quinolinolato andbenzoquinolinolato functional organics. Suitable examples of oxadiazolederivatives include, e.g.,2-(4-biphenylyl)-5-(p-tert-butylphenyl)-1,3,4-oxadiazole (PBD);2,2′-(1,3-phenylene)bis[5-[4-(1,1-dimethylethyl)phenyl]]-1,3,4-oxadiazole (CAS#138372-67-5); and1,3-Bis(4-(4-diphenylamino)-phenyl-1,3,4-oxidiazol-2-yl)-benzene (CAS#184101-39-1). Suitable examples of triazole derivatives (holeblocker-electron transporter) include, e.g.,3,4,5-triphenyl-1,2,4-triazole;3,5-bis(4-tert-butyl-phenyl)-4-phenyl-1,2,4-triazole; and3-(4-biphenylyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole. Suitableexamples of phenanthroline derivatives include, e.g.,2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP; CAS #4733-39-5).Suitable examples of quinolinolato and benzoquinolinolato complexesinclude, e.g., tris(8-hydroxyquinolinolato)aluminum (Alq₃);bis(10-hydroxybenzo[h]quinolinolato)beryllium (Bebq₂);2,2′,2″-(1,3,5-benzenetriyl)tris-[1-phenyl-1H-benzimidazole] (TPBI); andcyano substituted oligophenylenevinylene derivatives.

Mixtures of two or more of the electroluminescent materials in thepolymer matrix are contemplated to achieve specific colors or optionallyto yield white light.

The molecular weight of the electroluminescent material is preferablyless than 2000 amu (i.e., the electroluminescent material is preferablya low molecular weight substance). Higher molecular weight species wouldbe expected to have limited miscibility with many of the higher T_(g)polymers.

Light Emitting Device Structure

The construction of light emitting devices of the invention can begreatly varied. For example, suitable light emitting devices can have atransparent anode placed on one side of an appropriate substrate. A holeinjection/transport layer is placed on top of the transparent anode andcan comprise both a hole injection layer and a hole transport layer. Ontop of the hole transport layer is the light emitting layer where holesand electrons combine to emit light. On top of the light emitting layeris the electron injection/transport layer and on top of this layer thecathode is positioned. The anode, light emitting and cathode layers arerequired. The hole injection, hole transport, electron injection andelectron transport layers are optional. In specific cases where the holetransport or electron transport is too rapid, hole or electron blockinglayers can be provided to assure maximum electron-hole combination inthe light emitting layer.

Typically the substrate coated with the anode is glass. Transparentpolymer sheets and films can also be employed. These include, e.g.,Bisphenol A polycarbonate, PMMA, poly(ethylene terephthalate) film,polysulfone films, polypropylene films and the like.

The transparent anode is preferably indium-tin oxide (ITO), tin oxide ordoped zinc oxide. Conductive polymeric materials can be used as theanode or as a coating on the anode to improve hole injection. Theseinclude but are not limited to poly(3,4-ethylenedioxythiophene) dopedwith poly(styrene sulfonic acid) or other appropriate dopants andsulfonated polyaniline derivatives or polyaniline variants doped withstrong organic acids.

The hole transport layer includes but is not limited topolyvinylcarbazole, aromatic tertiary amines and phthalocyanines. Incertain embodiments, the hole transport layer can be comprised of lowmolecular weight compounds noted above in the discussion ofelectroluminescent materials along with higher molecular weight versionsof similar compounds.

The electron transport/injection layer can comprise low molecular weightcompounds such as the metal complexes of 8-hydroxyquinoline, triazolesor higher molecular weight polymers comprising oxadiazole, quinoxalineor triazole groups. In certain embodiments, the electron transport layercan be comprised of low molecular weight compounds noted above in thediscussion of electroluminescent materials along with higher molecularweight versions of similar compounds.

The metal cathode can comprise at least one member selected from thegroup consisting of calcium, magnesium, aluminum, silver and indium.When more than one of the group members is present, they can be mixed orlayered. Alloys with other metals can be employed and alkali or alkalineearth metals such as Cs and Li (as CsF and LiF) can be employed in minoramounts. The light emitting layer of this invention is preferablypositioned between the hole injection/transport layer and the electroninjection/transport layer in the foregoing preferred embodiment.

Alternatively, a single multifunctional layer can substitute for atleast two of the hole injection/transport layer, the electroninjection/transport layer and the light emitting layer. In certainembodiments of this invention, the hole transport, electron transportand light emitting materials can all be combined with the high T_(g)polymer in the light emitting layer to thereby provide a single layer(between the electrodes) device. This offers significant fabricationadvantages over multilayer devices. This specific feature of thisembodiment of the invention is quite important, because of theimportance of balancing hole and electron transport in a light emittingdevice so that the recombination of holes and electrons occurs at theproper position in the device. The combination of hole transport,electron transport and light emitting materials in the high T_(g)polymer of this invention can facilitate optimization of the lightemitting device.

In production of the light emitting device, the hole injection layer ofa transparent conducting polymer (e.g., polyethylenedioxythiophene orPEDOT) can be applied via spin coating, spray coating, meniscus coating,screen printing, ink jet printing or roll-to-roll processing. Lowmolecular weight hole injection materials can be applied usingsputtering or evaporative coating techniques. The hole transport layercan be applied by vacuum deposition as well as the other methods notedfor the hole injection layer. The light emitting layer comprising highT_(g) amorphous polymers with miscible low molecular weightelectroluminescent materials can be applied from an appropriate solventvia spin coating, ink jet printing, screen printing or roll-to-rollprinting processes. The electron transport/injection layer(s) can beapplied via vacuum deposition or the methods noted for the lightemitting layers. The cathode can be applied via sputtering or thermalvacuum evaporation/deposition techniques well known in the art as wellas screen printing, ink-jet printing or roll-to-roll processing.

The specific construction of the light emitting device to deliver amulticolor display panel required for many potential applicationsinvolves pixel design such that red, green and blue light emittingpixels can be employed to provide a full color spectrum. An advantage ofthe combination of high T_(g) polymers with low molecular weightelectroluminescent species is that it allows for preventing migration ofspecies from one pixel into neighboring pixels resulting in loss ofcolor definition with time. This combination should lead to increasedstability with high temperature exposure and should exhibit longerlifetimes without loss of luminescence or color definition.

A preferred LED device of this invention is a flexible flat paneldisplay. As used herein, the term “flexible” means that the flexibleobject (e.g., flat panel display) can be placed on a cylindricalcurvature of a cylinder having a radius of 6 inches without fracture ofthe device and without loss of its ability to exhibit light emission asin the flat state.

For the LED devices of this invention most of the compositions employedfor the cathode materials will be sensitive to water and/or oxygen.Other layers and materials utilized in the construction could also besensitive to water and oxygen exposure. For rigid devices, glasscoatings on both sides with proper sealants to prevent water or oxygendiffusion into the device will suffice. For flexible devices, flexiblebarrier films will need to be employed. For the non-transparent side ofthe device, flexible barrier films such as metallized poly(ethyleneterephthalate) could be employed. For the transparent side, flexibletransparent barrier films could be utilized, such as in BARIXencapsulation coatings available from Vitex corporation, and in U.S.Pat. No. 6,268,695 to Affinito.

In preparing light emitting devices of the invention, it is preferred topurify the non-electroactive polymer and the solvents employed in thesolution utilized to prepare the light emitting layer of the lightemitting device. The removal of ionic species (e.g., Na⁺, Li⁺, K⁺, Ca⁺⁺,Mg⁺⁺, Cu⁺, Cu⁺⁺ and the like) as well as the counterions (e.g. Cl⁻, Br⁻,SO₄ ⁻, CO₃ ⁻, etc.) is preferred to assure the efficiency of the deviceas well as assure quality control of the light emitting layer fromdevice to device. Coagulation of the polymer solution in a non-solventfollowed by rinsing, extraction of ionic species using ion-exchangeprocedures, addition of chelation agents and the like are possiblemethods for reducing the contaminant levels to acceptable levels. Theionic contamination is a particular problem with many condensationpolymers potentially employable in this invention.

The invention will be illustrated in more detail with reference to thefollowing Examples, but it should be understood that the presentinvention is not deemed to be limited thereto.

EXAMPLES

The first series of examples to demonstrate this invention involvedpreparing dilute solutions of fluorescent dyes and high T_(g) polymersin a common solvent. The samples (Examples 1-14) were prepared andmodest heating (up to 80° C. for higher boiling solvents) was employedto improve solubility. Examples 1-14 are summarized in Table 1 below.Solution value Film value Example Ingredients Property (nanometers)(nanometers)  1 0.1078 grams 5(6) carboxyfluorescein Visible λ_(max) 394460 0.3417 grams of polysulfone Excitation λ_(max) 402 472    40 gramsof NMP Emission λ_(max) 513 528  2 0.2329 grams of 5(6)carboxyfluorescein Visible λ_(max) 390 459 0.2309 grams of poly(phenylsulfone) Excitation λ_(max) 400 470    40 grams of NMP Emission λ_(max)510 526  3 0.1043 grams of Coumarin 343 Visible λ_(max) 443 439 0.1546grams of polysulfone Excitation λ_(max) 446 440    40 grams of NMPEmission λ_(max) 495 504  4 0.2408 grams of Coumarin 6 (Control) Visibleλ_(max) 464 452    40 grams of NMP Excitation λ_(max) 472 475 Emissionλ_(max) 504 547  5 0.2550 grams of Coumarin 6 Visible λ_(max) 464 4520.2410 grams of PAE-2 Excitation λ_(max) 470 470    40 grams ofcyclopentanone Emission λ_(max) 504 561  6 0.2482 grams of Coumarin 6Visible λ_(max) 464 452 0.2396 grams of poly(phenyl sulfone) Excitationλ_(max) 470 470    40 grams of cyclopentanone Emission λ_(max) 504 567 7 0.1705 grams of Rhodamine B Visible λ_(max) 560 576 0.1520 grams ofPAE-2 Excitation λ_(max) 564 529    30 grams of cyclopentanone Emissionλ_(max) 588 605  8 0.1586 grams Rhodamine B Visible λ_(max) 562 5450.1707 grams polysulfone Excitation λ_(max) 530 530    40 grams of NMPEmission λ_(max) 592 595  9 0.1500 grams Rhodamine B Visible λ_(max) 562549 0.1546 grams poly(phenyl sulfone) Excitation λ_(max) 530 530    40grams of NMP Emission λ_(max) 590 597 10 0.1555 grams Rhodamine BVisible λ_(max) 561 530 0.1667 grams of polystyrene Excitation λ_(max)530 530    40 grams of NMP Emission λ_(max) 590 586 11 0.1458 grams ofRhodamine B (control) Visible λ_(max) 561 527    40 grams of NMPExcitation λ_(max) 530 530 Emission λ_(max) 590 592 12 0.1163 grams ofCoumarin 334 Visible λ_(max) 454 381 0.1282 grams of poly(phenylsulfone) Excitation λ_(max) 456 374    30 grams of NMP Emission λ_(max)499 530 13 0.1074 grams of Coumarin 334 (control) Visible λ_(max) 454455    30 grams of NMP Excitation λ_(max) 440 440 Emission λ_(max) 499578 14 0.1310 grams of Coumarin 334 Visible λ_(max) 444 377 0.1306 gramsof polysulfone Excitation λ_(max) 440 374    40 grams of tetrahydrofuranEmission λ_(max) 481 532

All solution samples were run in 10×10 mm cuvettes for absorbance andphotoluminescence. The liquid samples were diluted with the appropriatesolvent to bring the absorbance maximum in the visible to less than 0.8a.u. to remove nonlinear distortions in both the absorbance andphotoluminescence signals.

Absorbance spectra were obtained with a Hitachi U-3110spectrophotometer. Bandpass was 2 nm, scan speed was 300 nm/min, scaninterval was 2 nm. A cuvette with the appropriate solvent was placed inthe reference beam for liquid samples, a clean silica disk or glassslide was placed in the reference beam for dried film samples.

Photoluminescence spectra were measured using a Hitachi F-2000fluorescence spectrometer with a high pressure Xe lamp source. Bandwidthwas 10 nm on both exitation and emission spectrographs. Film sampleswere placed at 45 degrees to source and emission with front surfaceillumination.

Example 15 Construction and Testing of an LED Device

An unpolished float glass SiO₂ slide (50×75×1.1 mm) coated on one sidewith indium tin oxide (resistance =8-12 ohms) had conductive silverpaste (colloidal silver paste from Ted Pella, Inc.) applied to oppositeends (75 mm apart) on the ITO coated slide of ˜0.5 cm². Aftersolidification of the silver paste, the slide was placed in a spin bowlapparatus (Laurell Model WS-400-8FTM-Full/HPD) and cleaned withisopropanol while spinning. A solution of Baytron P(3,4polyethylenedioxythiophene-polystyrene sulfonate (CAS#1555090-83-8)) solution in water (1.3 wt % solids) was obtained fromBayer and filtered through a 1 μfilter and applied to the ITO coatedglass slide surface and spun at 2000 rpm for 45 seconds. The sample wasallowed to dry and then approximately 1 ml of a solution of 0.4179 gramsof Rhodamine B, 0.4152 grams of polysulfone (P-1700 from Amoco), and 40grams of CHCl₃ was applied to the coated glass slide at 1000 rpm. Thesample was then masked and Al cathode sections were applied via thermalvacuum evaporation. The ends of the Al cathodes were coated with theconductive silver paste noted above. After drying and setting in alaboratory for several weeks (50% RH, 23° C.), the anode and cathodeswere connected to a voltage source and 20 volts and 40 volts wereapplied across the device.

Light emission was observed which was quite intense at 40 volts. Lightemission was only observed over the Al area coated with the conductivesilver paste. Later analysis indicated the Al cathode thickness was toolow to yield conductivity where the paste was not applied.

Example 16 LED Device Fabrication

An unpolished float glass SiO₂ slide (50×75×1.1 mm) coated on one sidewith indium tin oxide (resistance=8-12 ohms) was exposed to ozone for 20minutes and then had conductive silver paste (colloidal silver pastefrom Ted Pella, Inc.) applied to opposite ends (75 mm apart) on the ITOcoated slide of ˜0.5 cm². After solidification of the silver paste, theslide was placed in a spin bowl apparatus (Laurell ModelWS-400-8FTM-Full/HPD). Approximately 1 ml of a solution of 0.2550 gramsof Coumarin 6 and 0.2410 grams of PAE-2 dissolved in 40 grams ofcyclopentanone (filtered through a 0.45μ filter) was spin coated ontothe glass slide (1000 rpm for 45 sec.).

Example 17 LED Fabrication

An unpolished float glass SiO₂ slide (50×75×1.1 mm) coated on one sidewith indium tin oxide (resistance=8-12 ohms) was exposed to ozone for 20minutes and then had conductive silver paste (colloidal silver pastefrom Ted Pella, Inc.) applied to opposite ends (75 mm apart) on the ITOcoated slide of ˜0.5 cm². After solidification of the silver paste, theslide was placed in a spin bowl apparatus (Laurell ModelWS-400-8FTM-Full/HPD). A solution of Baytron P (3,4polyethylenedioxythiophene-polystyrene sulfonate (CAS #1555090-83-8))solution in water (1.3 wt % solids) was obtained from Bayer, dilutedwith an equal volume of distilled water and filtered through a 1 μfilterand applied to the ITO coated glass slide surface and spun at 1000 rpmfor 45 seconds. The glass slide was then heated at 125° C. for 5 minutes(under glass covers) in an air-circulating oven. After cooling,approximately 1 ml of a solution of 0.1705 grams of Rhodamine B and0.1520 grams of PAE-2 dissolved in 30 grams of cyclopentanone (filteredthrough a 0.45 μfilter) was spin coated on the glass slide at 1000 rpmfor 45 seconds. The sample was recoated with another 1 ml of the abovesolution for 45 sec at 1000 rpm.

Example 18 LED fabrication

An unpolished float glass SiO₂ slide (50×75×1.1 mm) coated on one sidewith indium tin oxide (resistance=8-12 ohms) was exposed to ozone for 20minutes and then had conductive silver paste (colloidal silver pastefrom Ted Pella, Inc.) applied to opposite ends (75 mm apart) on the ITOcoated slide of ˜0.5 cm². After solidification of the silver paste, theslide was placed in a spin bowl apparatus (Laurell ModelWS-400-8FTM-Full/HPD). Approximately 1 ml of a solution of 0.1705 gramsof Rhodamine B and 0.1520 grams of PAE-2 dissolved in 30 grams ofcyclopentanone (filtered through a 0.45 μfilter) was spin coated on theglass slide at 1000 rpm for 45 seconds.

Example 19 Demonstration of Thin Film Characteristics

A sample of Example 14 (0.1310 grams Coumarin 334/0.1306 grams ofpolysulfone/40 grams of tetrahydrofuran) was cast in a Petri dish anddevolatilized at room temperature. The resultant film, which had goodadhesion to glass, was removed by immersion in water. The very thin filmhad mechanical strength even though it was less than 50 wt. % of thepolymer. A dynamic mechanical analysis showed a glass transitiontemperature of approximately 50° C. with a clear indication thatresidual solvent (THF) was left in the film. Thus the dry film wouldhave a T_(g)>50° C. The observation that the film was transparent,amorphous and had mechanical durability indicates that the combinationsof high T_(g) polymers with high loading of electroluminescent lowmolecular weight compounds are quite suitable for FOLED fabricationprocesses.

Example 20 Determination of T_(g) of Polymer/Fluorescent Material Blend

A sample of 2 grams of polysulfone (P-3500) (obtained from Amoco) and 1gram of Coumarin 6 (obtained from Aldrich) were dissolved in 30 grams oftetrahydrofuran followed by devolatilization. The devolatilized film wascompression molded at 210-220° C. A sample of 3 grams of polysulfone(P-3500, Amoco) was also dissolved in 30 grams of tetrahyudrofuran anddevolatilized and compression molded at 230-240° C. The samples weresubmitted for dynamic mechanical analysis using a Rheometrics SolidAnalyzer (RSA II) with a deformation frequency of 6.28 rad/sec. TheT_(g) of the polysulfone was found to be initially 146° C. (indicatingresidual THF in the sample) which when fully devolatilized gave a T_(g)of 190° C., and the polysulfone/Coumarin 6 (2/1 blend) T_(g) was 132° C.The blend was transparent and appeared to be quite miscible.

The DSC results on the above blend were determined at a heating andcooling rate of 10° C./min.

The calorimetry results on the polysulfone/Coumarin 6 (2/1) blend castfrom tetrahydrofuran are listed below:

Coumarin 6 Control

-   -   1st heating: T_(m)=211.3° C.; ΔH_(f)=109.8 J/g    -   1st cooling: T_(c)=184.0° C.; ΔH_(c)=87.6 J/g    -   2nd heating: T_(m)=211.8° C.; ΔH_(f)=94.9 J/g

Polysulfone Control

-   -   1st heating: T_(g)=142.5° C.    -   1st cooling: T_(g)=166.2° C.    -   2nd heating: T_(g)=169.8° C.

Polysulfone/Coumarin 6 (2/1) Blend

-   -   1st heating: T_(g)=100.4° C.; T_(c)=159.3; ΔH_(c)=16.3 J/g;        T_(m)=190.7° C.; ΔH_(f)=18.2 J/g    -   1st cooling: T_(g)=107.0° C.    -   2nd heating: T_(g)=110.4° C.; T_(c)=183.3° C.; ΔH_(c)=0.75 J/g;        T_(m)=197.0° C.; ΔH_(f)=0.82 J/g

The DSC results also show the depression of the polysulfone T_(g) due toresidual THF. The cooling data and 2nd heating data show an increasedT_(g) due to THF devolatilization from the sample. Thepolysulfone/Coumarin 6 blend sample shows the sample is amorphous asprepared but crystallizes during the temperature excursion ofcalorimetry testing when the temperature exceeds the T_(g) of the blend.The cooling curve does not exhibit any Coumarin 6 crystallization forthe blend but prominent crystallization for the control Coumarin 6. The2nd heating curve shows a very modest level of Coumarin 6crystallization when heated well above the sample T_(g). A rapiddevolatilization of solvent from a polysulfone/Coumarin 6 blend willresult in an amorphous thin film with a T_(g) well above the valuesnoted to offer problems (˜75° C.) for LED applications. The DMA and DSCresults clearly demonstrate that the laser dyes (e.g., Coumarin 6) showgreatly depressed crystallization rates with incorporation in high T_(g)polymers such as polysulfone.

Example 21

A solution was prepared by dissolving 35.5 mg of PAE-2, 16.2 mg ofN,N′-Bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD, CAS #65181-78-4),and 0.9 mg of Coumarin 6 (CAS #38215-36-0) in 2.61 grams ofchlorobenzene. A polished soda lime float glass (2.5×2.5×0.7 cm) coatedon one side with indium tin oxide (sheet resistance ≦15 ohms per square)was cleaned by ultrasonication sequentially in detergent, de-ionizedwater, methanol, isopropanol, and acetone; each for 5 min. The ITOcoated glass substrate was allowed to dry between different solvents.After being exposed to UV-ozone for 10 min, the ITO glass substrate wasplaced on the chuck of a Laurell Model WS-400-N6PP spinner and thesolution was applied to it at a spin rate of 1200 rpm. The sample wasthen masked and Mg/Ag layers were sequentially deposited via thermalvacuum evaporation at a pressure less than 1×10⁻⁵ Torr. Under forwardbias (ITO connected to positive and Ag connected to negative electrode),green light emission was observed above 14 V and became very bright at25 V. FIG. 1 shows the current-voltage characteristic of the device.

Example 22

A solution was prepared by dissolving 35.4 mg of PAE-2, 16.0 mg of2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD, CAS#15082-28-7) and 0.8 mg of Coumarin 6 (CAS #38215-36-0) in 2.59 grams ofchlorobenzene. A polished soda lime float glass (2.5×2.5×0.7 cm) coatedon one side with indium tin oxide (sheet resistance ≦15 ohm per square)was cleaned by ultrasonication sequentially in detergent, de-ionizedwater, methanol, isopropanol, and acetone; each for 5 min. The ITOcoated glass substrate was allowed to dry between different solvents.After being exposed to UV-ozone for 10 min, the ITO glass substrate wasplaced on the chuck of a Laurell Model WS-400-N6PP spinner and thesolution was applied to it at a spin rate of 1200 rpm. The sample wasthen masked and Mg/Ag layers were sequentially deposited via thermalvacuum evaporation at a pressure less than 1×10⁻⁵ Torr. Under forwardbias (ITO connected to positive and Ag connected to negative electrode),green light emission was observed above 22 V and became very intense at38 V. FIG. 2 shows the current-voltage characteristic of the device.

Example 23

A solution was prepared by dissolving 20.4 mg of PAE-2, 5.3 mg ofN,N′-Bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD, CAS #65181-78-4),6.5 mg of 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD,CAS #15082-28-7) and 0.8 mg of Coumarin 6 (CAS #38215-36-0) in 1.60grams of chlorobenzene. A polished soda lime float glass (2.5×2.5×0.7cm) coated on one side with indium tin oxide (resistance ≦15 ohms persquare) was cleaned by ultrasonication sequentially in detergent,de-ionized water, methanol, isopropanol, and acetone; each for 5 min.The ITO coated glass substrate was allowed to dry between differentsolvents. After being exposed to UV-ozone for 10 min, the ITO glasssubstrate was placed on the chuck of a Laurell Model WS-400-N6PP spinnerand the solution was applied to it at a spin rate of 1200 rpm. Thesample was then masked and Mg/Ag layers were sequentially deposited viathermal vacuum evaporation at a pressure less than 1×10⁻⁵ Torr. Underforward bias (ITO connected to positive and Ag connected to negativeelectrode), green light emission was observed above 18 V and became verybright at 38 V. FIG. 3 shows the current-voltage characteristic of thedevice.

Example 24

A solution was prepared by dissolving 19.7 mg of PAE-2, 7.8 mg of4-(Dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM,from Aldrich, CAS #51325-91-8) in 1.0781 g of chlorobenzene and filteredwith a 0.2 μm hydrophobic filter. A polished soda lime float glass(2.5×2.5×0.7 cm) coated on one side with indium tin oxide (resistance≦15 ohms per square) was cleaned by ultrasonication sequentially indetergent, de-ionized water, methanol, isopropanol, and acetone; eachfor 5 min. The ITO coated glass substrate was allowed to dry betweendifferent cleaning solvents. After being exposed to UV-ozone for 10 min,the ITO glass substrate was placed on the chuck of a Laurell ModelWS-400-N6PP spinner and a water based dispersion ofpoly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid (PEDOT,diluted from the original solid contents of about 1.3 wt % of Baytron Pfrom Bayer Corporation to ˜0.5 wt % using de-ionized water) was appliedto it at a spin rate of 1200 rpm. Then the PEDOT coated sample was putin a vacuum oven (˜25 mmHg) and annealed at 80° C. for 10 min. Afterthat, the annealed sample was placed on the chuck of the spinner and thesolution of PAE-2:DCM was applied to it at a spin rate of 1200 rpm.Finally the sample was masked and Mg/Ag layer were sequentiallydeposited via thermal vacuum evaporation at a pressure less than 1×10⁻⁵Torr. Under forward bias (ITO connected to positive and Ag connected tonegative electrode), red light emission was observed above 18 V andbecame very bright at 30 V. FIG. 4 shows the current-voltagecharacteristic of the device. The current of the device was reasonablyhigh, suggesting that the blending ratio of DCM (28.4 w % of thePAE-2:DCM film) had reached the percolation ratio needed for conductingcurrent.

Example 25

Four solutions of Coumarin 6 (CAS #38215-36-0) doped blends of PAE-2 andhole transporting materialN,N′-Bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD, CAS #65181-78-4)were prepared as follows. Solution 1: 19.0 mg of PAE-2 and 1.0 mg of TPDplus 0.3 mg of Coumarin 6 dissolved in 1.00 g of chlorobenzene. Solution2: 18.0 mg of PAE-2 and 2.0 mg of TPD plus 0.3 mg of Coumarin 6dissolved in 1.00 g of chlorobenzene. Solution 3: 17.0 mg of PAE-2 and3.0 mg of TPD plus 0.3 mg of Coumarin 6 dissolved in 1.00 g ofchlorobenzene. Solution 4: 16.0 mg of PAE-2 and 4.0 mg of TPD plus 0.3mg of Coumarin 6 dissolved in 1.00 g of chlorobenzene. The blendingratios of TPD in Solution 1, 2, 3 and 4 were 5 wt %, 10 wt %, 15 wt %,and 20 wt %, respectively. The solutions were filtered with a 0.2 micronhydrophobic filter.

Four polished soda lime float glass (2.5×2.5×0.7 cm) substrates coatedon one side with indium tin oxide (resistance less than 15 ohm/square)were cleaned by ultrasonication sequentially in detergent, de-ionizedwater, methanol, isopropanol, and acetone; each for 5 min. The ITOcoated glass substrates were allowed to dry between different cleaningsolvents. After being exposed to UV-ozone for 10 min, the ITO glasssubstrates were placed on the chuck of a Laurell Model WS-400-N6PPspinner and the solutions were applied to them at a spin rate of 1200rpm, one solution on one substrate. The samples were then masked andMg/Ag layers were sequentially deposited via thermal vacuum evaporationat a pressure less than 1×10⁻⁵ Torr. Under forward bias (ITO connectedto positive and Ag connected to negative electrode), green lightemission was observed. FIG. 5 shows the current-voltage characteristicsof the four devices. As the weight ratio of TPD increased to 15 wt %,the current passed through the device dramatically increased. Hence thepercolation threshold of TPD in PAE-2 is around 15 wt %.

Example 26

A solution was prepared by dissolving 15.5 mg ofpoly(2,6-dimethyl-1,4-phenylene oxide), 5.9 mg ofN,N′-Bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD, CAS #65181-78-4),and 0.3 mg of Coumarin 6 (CAS #38215-36-0) in 1.00 grams chlorobenzene.The solution was filtered with a 0.2 micron hydrophobic filter. Apolished soda lime float glass (2.5×2.5×0.7 cm) coated on one side withindium tin oxide (resistance less than 15 ohm/square) was cleaned byultrasonication sequentially in detergent, de-ionized water, methanol,isopropanol, and acetone; each for 5 min. The ITO coated glass substratewas allowed to dry between different cleaning solvents. After beingexposed to UV-ozone for 10 min, the ITO glass substrate was placed onthe chuck of a Laurell Model WS-400-N6PP spinner and the solution wasapplied to it at a spin rate of 1200 rpm. The sample was then masked andMg/Ag layers were sequentially deposited via thermal vacuum evaporationat a pressure less than 1×10⁻⁵ Torr. The active area of the device wasabout 6 mm². Under forward bias (ITO connected to positive and Agconnected to negative electrode), light emission was observed above 25V. FIG. 6 shows the current-voltage characteristic of the device.

While the invention has been described in detail and with reference tospecific examples thereof, it will be apparent to one skilled in the artthat various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof.

1. A method for manufacturing a light emitting device comprising:providing a light emitting layer comprising an electroluminescentorganic material dispersed in a matrix, wherein the electroluminescentorganic material has a molecular weight less than about 2000 amu, thematrix comprises a non-electroluminescent organic polymer having a T_(g)of at least 170° C., and each of the non-electroluminescent organicpolymer and the electroluminescent organic material constitutes at least20 percent by weight of the light emitting layer; and providingelectrodes in electrical communication with the light emitting layer,wherein the electrodes are configured to conduct an electric chargethrough the light emitting layer such that the light emitting layeremits light.
 2. The method of claim 1, wherein the light emitting layerproviding comprises at least one thin layer fabrication techniqueselected from the group consisting of spin coating, screen printing, inkjet printing and roll-to-roll printing.
 3. The method of claim 2,wherein one of the electrodes is an anode and the other of theelectrodes is a cathode, the anode is provided on a first side of thelight emitting layer, the cathode is provided on a second side of thelight emitting layer, and a transparent substrate is provided on a sideof the anode facing away from the light emitting layer.
 4. The method ofclaim 3, further comprising providing a hole transport layer between theanode and the light emitting layer and an electron transport layerbetween the light emitting layer and the cathode.
 5. The method of claim4, wherein the hole transport layer providing comprises at least onethin layer fabrication technique selected from the group consisting ofspin coating, spray coating, meniscus coating, ink jet printing,roll-top-roll processing screen printing, sputtering, evaporativecoating and vacuum deposition.
 6. The method of claim 5, wherein theelectron transport layer providing comprises at least one thin layerfabrication technique selected from the group consisting of vacuumdeposition, spin coating, screen printing, ink jet printing androll-to-roll printing.
 7. The method of claim 6, wherein the providingof the electrodes comprises at least one member selected from the groupconsisting of sputtering, screen printing, ink jet printing,roll-to-roll printing, thermal vacuum evaporation and thermal vacuumdeposition.
 8. The method of claim 4, wherein the light emitting layer,the hole transport layer and the electron transport layer are providedby printing.
 9. The method of claim 2, wherein thenon-electroluminescent organic polymer is a poly(arylene ether).
 10. Themethod of claim 9, wherein the poly(arylene ether) comprises repeatingunits of the structure:—(—O—Ar¹—O—Ar²—)m—(—O—Ar³—O—Ar⁴—)n— wherein m is 0 to 1, n is 1-m andAr¹, Ar², Ar³ and Ar⁴ are independently divalent arylene radicals. 11.The method of claim 10, wherein Ar¹, Ar², Ar³ and Ar⁴ are divalentarylene radicals independently selected from the group consisting of:

provided that Ar¹, Ar², Ar³ and Ar⁴ cannot be isomeric equivalents otherthan diradical 9,9-diphenylfluorene.
 12. The method of claim 10, whereinm is 0.5 and n is 0.5.
 13. The method of claim 10, wherein m is 1 andAr¹ is biphenyl radical.
 14. The method of claim 2, wherein thenon-electroluminescent organic polymer ispoly-2,6-dimethyl-1,4-phenyleneoxide.
 15. The method of claim 2, whereinthe T_(g) of the non-electroluminescent organic polymer is at least 200°C.
 16. The method of claim 2, wherein the non-electroluminescent organicpolymer constitutes not more than 50 percent by weight of the lightemitting layer.
 17. The method of claim 2, wherein theelectroluminescent organic material constitutes at least 50 percent byweight of the light emitting layer.
 18. The method of claim 2, whereinthe electroluminescent organic material is at least one member selectedfrom the group consisting of distyrenyl derivatives, Coumarin 6,Coumarin 334, Coumarin 343, Rhodamine B, Rhodamine 6G, Rhodamine 110,Fluorescein 548, 2′,7′-dichlorofluorescein, cresyl violet perchlorate,Nile Blue AA perchlorate, p-terphenyl, p-quaterphenyl, Exalite (376,384r, 389), Fluorol 555, Fluorescein Diacetate, Carbostyril 165, IR-140,Thionin, perylene, 9-amino acridine HCl and aromatic methylidinecompounds of the general structure:R¹R²C═CH—Ar—CH═CR³R⁴ where Ar is an aromatic structure, and R¹, R², R³,and R⁴ independently represent hydrogen, alkyl groups, alkoxy groups,aromatic groups including substituted aromatic groups or cycloaliphaticgroups.
 19. The method of claim 2, wherein the electroluminescentorganic material is at least one member selected from the groupconsisting of naphthalene derivatives, anthracene derivatives,phenanthrenes, perylenes, chrysenes, butadienes, periflanthenes andtetravinylpyrazines.
 20. The method of claim 2, wherein the lightemitting device is provided with sufficient flexibility to be contouredaround a cylinder with a radius of six inches without fracture or lossof light emitting capabilities.